1. Field of the Invention
This invention relates to modeling pastes.
2. Introduction to the Invention
Model-making is an important industrial activity. For example, in the automotive, aerospace and other industries, it is necessary to produce prototype designs before committing to full-scale production. One long-established method of making such prototypes uses model (or styling) boards. Model boards are typically 50 to 100 mm (2-4 inch) thick and up to 1.5 m (60 inch) long, and are composed of a filled polymeric material which can be easily machined. A number of model boards (which may be preshaped) are joined together with adhesive to make a preform which has the same general shape as the model, but is somewhat larger, and which is machined into the desired model. Problems with this method include the need to maintain a large inventory of model boards, the wasteful use of modeling material, the weight of the model, and the presence on the model of bond lines and voids between model boards. In a second method, a curable modeling material is applied as a thick layer to a preform which has the same general shape as the model but is somewhat smaller, and is cured in place before being machined into the shape of the model. This second method poses very serious problems in formulating a modeling material which will remain in place on the preform while it is being cured. Attempts to overcome these problems have been expensive and only partially successful. In one such attempt, a thermosetting paste is prepared in a meter, mix and dispensing (MMD) machine, and is immediately applied to the preform. However, MMD machines are difficult and expensive to operate and maintain, particularly on the intermittent basis needed in model-making. Furthermore, MMD machines cannot mix pastes containing the high proportions of fillers which are desirable in order to control the slump of the paste after it has been applied to the preform and before it sets up. In a variation of this method, a modeling paste produced by an MMD machine is frozen in the form of a sheet and is applied to the preform at a later time. However, even when frozen, such sheets have a limited shelf life, and air often is trapped between adjacent sheets when they are applied to the preform.
Thermosetting epoxy resin systems, and other crosslinkable resin systems, are well known. It is known that in order to produce such a system which is relatively stable in storage, one of the active chemical moieties (e.g. a catalytic moiety or a reactive moiety) can be present in a "latent" form, which can be activated (by heating or otherwise) when rapid reaction is desired. Reference may be made for example to U.S. Pat. Nos. 4,349,651, 4,358,571, 4,420,605, 4.430,445, 4,659,779, 4,689,388, 4,701,378, 4,742,148 and 4,933,392 and European Patent Publication No. 362787A2. Commonly assigned U.S. application Ser. Nos. 08/726,739, abandoned 08/726,740 abandoned and 08/726,741 pending (each of which has been abandoned in favor of copending, commonly assigned, continuation-in-part application Ser. No. 09/216,520, and each of which was filed Oct. 15, 1996 and claims priority from U.S. application Ser. No. 08/399,724 filed Mar. 7, 1995, now abandoned) and corresponding International Application No. PCT/US96/03023 (published Sep. 12, 1996, as International Publication No. WO-96/27641) disclose particularly valuable latent materials comprising an active chemical moiety which is bonded to a side chain crystalline (SCC) polymer or to another crystalline polymeric moiety which melts over a narrow temperature range. These latent materials, which are referred to in the applications as polymeric modifying agents, are preferably in the form of particles having an average size of 0.1 to 50 microns. Copending, commonly assigned U.S. application Ser. No. 08/710,161 (Docket No. 10762-4 filed Sep. 12, 1996), which has now been abandoned, also in favor of copending commonly assigned application Ser. No. 09/216,520 referred to above, abandoned and corresponding International Application No. PCT/US 97/16019 (which was not published at the date of this application), but was published on Mar. 19, 1998, as International Publication No. WO 98/11166 disclose that even when there is no chemical bond between the active and polymeric moieties, a physical bond between the moieties can produce a lesser but still useful latent effect.
The disclosure of each of the U.S. patents and patent applications and International and European patent publications referred to in the preceding paragraph is incorporated herein by reference for all purposes.